Polymers of carbon monoxide and ethylenically unsaturated hydrocarbons have been known for some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical initiators, e.g., peroxy compounds. U.K. 1,081,304 discloses the production of similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium salts as catalyst. Nozaki extended this reaction to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See, for example, U.S. Pat. No. 3,689,460 and U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and ethylenically unsaturated hydrocarbons has become of greater interest in part because of the greater availability of the polymers in quantity. Production of this class of polymers, also known as polyketones or polyketone polymers, is illustrated by a number of Published European Applications including 121,965 and 181,014 and by copending U.S. patent application Ser. No. 930,468 filed Nov. 14, 1986. These references illustrate the production of linear alternating polymers of carbon monoxide and ethylenically unsaturated hydrocarbons in the presence of catalyst compositions formed from a compound of palladium, cobalt or nickel, the anion of a non-hydrohalogenic acid having a pKa less than about 6, and a bidentate ligand of phosphorus, arsenic or antimony.
In general, these polymerization catalyst compositions are mixed with the monomers in an organic diluent in which the polymers are insoluble. During the polymerization process the polymers are obtained in the form of a suspension in the diluent. Generally, the polymerization is terminated by cooling and releasing the pressure after the required degree of polymerization is reached. The polymers can be isolated from the suspension for instance by filtration or centrifugation. Organic diluents that have been found very suitable are aliphatic alcohols having at most 10 carbon atoms in the molecule such as methanol, ethanol and propanol.
With a view to their uses, the polymers are more valuable when their molecular weights are higher. The molecular weights of the polymers can be influenced by the temperature at which the polymerization is carried out, in that at otherwise similar reaction conditions, a decrease in reaction temperature will lead to a higher molecular weight. However, a decrase in reaction temperature will be attended with two further effects. First, a decrease in reaction temperature will bring with it a fall in polymerization rate. Second, a decrease in reaction temperature will lead to a decreased polymer bulk density.
By replacing the alcohols partly or wholly with other diluents, such as aliphatic ketones having at most 10 carbon atoms in the molecule, aliphatic carboxylic acid esters, or aliphatic hydrocarbons, an increase in molecular weights could be attained as shown in U.S. Pat. No. 4,810,774, but this increase was in all known examples accompanied with a severe drop in polymerization rate and more often than not a fall in polymer bulk density was observed.